Rear brake imbalance - not balanced

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Stan3
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Rear brake imbalance - not balanced

Post by Stan3 »

Hi All!

Changed rear brake drums, shoes and wheel cylinders recently before MoT. Job went really well without colourful language! All bled well. Checked no binding and both sides pulled up feeling the same stopping by hand whilst someone else applied brakes. Handbrake pulled up nice & even.

Passed MoT in terms of stopping power but MoT man said there was was an imbalance between left & right, ie. majority of braking was being done by nearside. After running I notice that the nearside drum is too hot to touch whilst the offside is just warm (can easily rest fingers on). MoT man suggested the piston diameters could be different between the two wheel cylinders?? I fitted Pagid cylinders from Europarts.

Anyone heard of this? worried the heat may boil the brake fluid. Any other suggestions? Should I strip down again?

Thanks!
phil

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itchyfeet
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Re: Rear brake imbalance - not balanced

Post by itchyfeet »

usually shoes not centred properly ( they may not self centre) or adjusters not adusted evenly ( adjuster on each wheel)

I adjust then drive it then jack and readjust to get them pulling up equally. so one click check both. two clicks check both etc.

the centre adjuster is the last one to do once they pull up equally.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Thanks for responding Itchyfeet...think you’re referring to the handbrake balance...thing is that was ok, imbalance was on the pedal...?
Cheers
Phil

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

The adjuster affects the base position of the shoes...... and hence the footbrake.

If you can get two jacks it's easier to balance them both up at the same time

An alternate method is to adjust the brakes up (handbrake off) on the adjuster until they lock, and then back off an equal number of clicks. Make sure the drums are free and the handbrake operation is sufficient.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Ah....ok 937 will give it another go!
Thanks for your reply
Phil

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itchyfeet
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Re: Rear brake imbalance - not balanced

Post by itchyfeet »

Stan3 wrote:Ah....ok 937 will give it another go!
Thanks for your reply
Phil


well done 937 looks like you solved the problem.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Hi, ok, so have today jacked up rear, bled cylinders through for good measure, wound up both adjusters to solid and then back to (just) free spinning drums. Adjusted handbrake on the centre pull.

Went for a drive. Near side drum too hot to touch, offside just nice and warm to touch, no problem to keep your fingers on it....

Looks as though all (certainly loin’s share) of the braking power is going to the near side (this is what MoT man said), (though passed MoT as total braking power was ok)......MoT man said possibly wheel cylinder pistons could be different diameter (presumably he meant therefore exerting differing pressure?)? Anyone heard of this? Anymore ideas?

Head scratching Phil!

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

Different size wheel cylinders change the effective diameter of the shoes, so your MOT man could be right but who would have fitted a wrong one?

Did you back the handbrake off before adjusting ?

I would slacken the handbrake well off and redo. Are you sure the wheel bearings are both fine and not the cause of the heat ?

Get the rear brakes working correctly on the footbrake before bothering with the handbrake as well, when you have problems like this take one step at a time.

If the nearside remains hot back the adjuster off more

Are you sure the OSR linings are not contaminated. Oil on those means less friction and therefore less heat generated too. Remember brakes convert kinetic energy into heat.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Thanks 937

I fitted the wheel cylinders - both new Pagid from Europarts, they certainly look the same! MoT man said sometimes piston diameter can vary slightly even between same makes...?!

Both sides are equal in terms of free spinning so backing off the near side adjuster shouldn’t make any difference..?

As majority of braking power was NSR (as per MoT) it would seem logical this is accounting for difference in heat rather than wheel bearings?

Thanks
Phil

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937carrera
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Re: Rear brake imbalance - not balanced

Post by 937carrera »

Stan3 wrote: Both sides are equal in terms of free spinning so backing off the near side adjuster shouldn’t make any difference..?

So what if the NSR shoes were 1mm clear of the drum, and the OSR were 2mm from the drum after adjustment, for whatever reason.

What would be the effect on the brakes then ??

Sometimes you need to adjust to what works rather than "equal".

If the wheels spin freely with no play/noise and require similar effort then I think you can conclude the bearings are OK
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itchyfeet
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Re: Rear brake imbalance - not balanced

Post by itchyfeet »

did you pinch the flexi pipes with a clamp when fitting cylinders?, if you did they can collapse inside and turn into a one way valve.

I have had this myself before, brake and the brakes stay on for some time before slowly coming off.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Nope, brakes release as they should...

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Re: Rear brake imbalance - not balanced

Post by captain Byrne »

Check the back plate is straight & parallel to the wheel. It's easily bent when yanking the drum off if it's tight. Look at the end of the shoes where the pad joins the shoe, it should be wearing parallel. If the shoe is in any way wedge shaped you'll have a hot spot & although it doesn't feel tight when you spin the wheel to adjust, it'll be constantly rubbing & will get hot quickly. I had exactly the same problem & it took me ages to figure it out.
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Stan3
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Re: Rear brake imbalance - not balanced

Post by Stan3 »

Thanks CB, interesting, although not sure that would explain why braking pressure is greater on that side?
Phil

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itchyfeet
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Re: Rear brake imbalance - not balanced

Post by itchyfeet »

Pull the drums off and get a clear picture of both sides, something may just be obvious to somebody.
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